EVERY TRICK IN THE BOOK: Jay-Z is launching his first book, “Decoded,” with a scavenger hunt of sorts sponsored by search engine Bing — with Gucci in on the game. Pages of the book have been placed in various places meaningful to the hip-hop impresario, with clues revealed on Jay-Z’s Facebook and Twitter pages, Jay-Z.com and on a dedicated Bing site, with fans winning prizes for finding them. On Thursday, Gucci revealed two of the pages in the windows of its Fifth Avenue flagship, printed on the lining of a one-of-kind leather bomber jacket designed by creative director Frida Giannini. The display will remain on view until Nov. 16, when the book goes on sale — and then the jacket will be gifted to Jay-Z. Other places where pages from the book can be found include the bottom of the pool of the Delano hotel in Miami and underneath plates at the Spotted Pig restaurant in New York.